Gas "carbourator"

First let me point out this idea is not mine. It was designed and executed by the fellow enthusiast who visited me yesterday. He sent me those pictures so l can post them here in his name.

He converted his 2l Subaru engine on LPG, and designed this neat gas mixer.


It has a conical boddy and a conical slide under spring tension. The slide slides over a center pipe with holes drilled in. When the engine vacuum pulls the slide in, it opens a certain amount of holes that then suck the gas in.

Incredibly simple and it seems to work flawlessly.

l was under the impression the center pipe is pressurised but that is not the case. There is a vaporisator between the LPG tank and the gas mixer that vaporises the LPG via engine coolant heat and requires a vacuum to pull the gas out. This is where this system resembles woodgas…


That is very interesting. I assume that there is vacuum all the way back to the vaporizer? and regulator? So then when the engine stops there will be no vacuum so ambient pressure makes the regulator close and fuel stops?


Exactly, althugh he has a safety valve too.


Kristjan , hvala za objavo in lepo predstavitev, morada bo komu koristilo.

Še moja razlaga:
Želja je bila doseči, od prostega teka motorja (ko je pretok zraka najmanjši in je potrebno zelo fino dozirati plin), do polne obremenitve, kaj se da enakomerno mešanico gorivo zrak (1:16 ).
Osnova je venturi cev , v kateri sredini se nahaja gibajoč se element , ki ga pretok zraka potiska s seboj, tako presek pretočnega dela spreminja, hkrati pa tale gibajoč del deluje kot ventil , saj na cevki , po kateri drsi odpira večji ali manjši presek tudi plinu (izvrtine v cevki).
Sistem je popolnoma mehanski,od elektrike je edino preklopno stikalo, s katerim preklapljam tok iz bencinske črpalke na mag, ventile plina. Sedaj ko je izdelana geometrija in izvrtane primerne luknjice se dejansko nima kaj pokvarit ali “razštelat”, …

Podoben mešalnik imam v prihodnosti izdelat za lesni plin le da bo razmerje 1:1 , sam mislim , da bo omogočal stabilno in homogeno gorljivo zmes v širokem območju delovanja motorja

Christian, thanks for the post and a nice introduction, it must be helpful to anyone.

Still my explanation:
The desire was to achieve, from idling the engine (when the air flow is minimal and the gas needs to be fine-tuned), to full load, giving a uniform mixture of fuel air (1:16).
The base is a venturi tube, in which center there is a moving element, which the air flow pushes with itself, thus changing the cross section of the flowing part, and at the same time this moving part acts as a valve, since on the tube through which the slide opens a larger or smaller cross section gas (holes in the tube).
The system is completely mechanical, with electricity being the only switching switch by which I switch the flow from gas station to mag, gas valves. Now that the geometry has been worked out and the holes drilled, there is actually nothing to spoil or “crack” …

I have a similar blender for wood gas in the future except that the ratio will be 1: 1, I think it will allow a stable and homogeneous combustible mixture in a wide range of engine operation


Wood Gas Gas Mixer
The idea is similar to what I learned for LPG and it works really well, only to turn the logic around a bit here and condition the inlet of the air with the flow of gas for a purpose, because the resistance changes through the gas generator, cooler and filter. This mixer, in my opinion, will easily offset these problems. The advantage is even in a homogeneous mixture.

I ask for critical comments and suggestions


hi looks good some thought went into that valve i only have one question shouldnt the air go were the gas is and the gas go in the small pipe i dont know maybe i missed somthing . it looks somthing like a pcv valve on the crank case vent i am probly wrong .??? just scraching my brain


Tone, edina stvar ki me mogoče skrbi je koliko upora bo predstavljal ventil. To sploh ni problem pri stacionarnih enotah ali delovnih strojih ko moč načeloma ni problem, problem zna bit na mobilnih sistemih. Za konstantno vožnjo recimo 80-90kmh sicer ni problem ker se itak ne vozi s polnim gasom ampak pri pospeševanju je pa potreben vsak mililiter plina kar ga je motor zmožen vsrkat.

@JO_Olsson poroča opazno razliko že samo če pravočasno ne očisti sesalnega kolekrorja in dušilne lopute kjer se naberejo saje.

Ampak glede na to da si omenil da te zaenkrat predelava avta oz podobnega ne zanima mislim da bo delovalo super.

Larry, razporeditev je pravilna. Bolje je skozi gibajoč del vsrkavat zrak kot pa vlažen in včasih sajast plin ki bi utegnil povzročat težave.

Tone, only concern l see is the drag it may create. Not a problem cruising down the highway when you dont drive at WOT anyway but at acceleration you need every cubic inch motor can suck in.

@JO_Olsson reports great difference in power even if he doesent burn the intake in time.

But you did mention you are not interested in mobile applications for now so for a stationary system this shuld work great!

Larry, the arrangement is correct. Better to suck air trugh the delicate slideing plunger and nozzles thain wet and sooty woodgas.


Ena stvar edino… Ta mešalnik bo izničil oz omejil nihanja v uporu sistema, ne bo pa izničil nihanja kvalitete plina… Ampak ponovno, pri stacionarnih aplikacijah in konstantni porabi plina teh težav tudi praktično ni.

Razmišljam, če bi dodal pod vzmet še mehanizem za nastavitev napetosti vzmeti… Bi lahko s tem tudi spremenil razmerje?

A nother thing… This mixer wuld prevent or limit differences in drag on the sistem but what it doesent acount for is fluctuations in gas quality… But again not a problem on stationary systems where gas demand is more or less constant, thus gas quality is too.

I am thinking, wuld makeing the spring tension adjustible allso adjust a/f ratio in different demands?


Well, there’s not much buildup in the actual intake or intake runners. On and around the throttle plate, on the other hand, is where soot likes to accumulate.
It’s not like the gap around a wide open throttle is blocked enough to justify the lack of power or anything. It just seems the soot makes for less turbulence and mixing. This is why I agree with @Tone about the importance of a homogenous mixture.
I remember the reasons for buildup of soot, mainly on the downstream side of a throttle plate, has been discussed earlier. I guess anyone driving a gravel road can testify dust will accumulate on the lee side of any protrouding part of their vehicle. The reason being the sudden pressure difference, when gasses passes your throttle plate, is another way to put it. There was even talk about CO converting back to carbon due to that sudden difference.


Tone, Kristjan,
The propane carburetor uses a pressure regulator to control the flow of fuel. I think the WG carb will need a regulator to control the flow of air.


As l unerstand the principal is that the venturi effect is much stronger and linear thain the difference in drag.

The regulator in Tones lpg mixer actilualy needs a vacuum to give any gas. It doesent produce any pressure. The system relys on the ventury effect and changeing nozzles to achive a even mix.


Ne, ker z napetostjo vzmeti omejujemo tudi pretok plinu, tako kot je Rindert napisal, za to potrebujemo še korekcijsko loputo za zrak, no tu Kristjan , če bi naredil podoben element ,…

No, because with the tension of the springs, we also limit the flow of gas, just as Rindert wrote, we also need a correction hatch for the air, but here Christian, if he were to make a similar element, …